1. Field of the Invention
The present invention relates to a scanning probe microscope technology capable of shape measurement not affected by electrostatic charge distribution of a sample.
2. Description of the Related Art
As a measurement technology of a microscopic 3D shape, a scanning probe microscope (SPM) has been known. The SPM, employing a technology of scanning a sample while a cantilever having a pointed probe is being controlled and a contact force is being kept at a very small value, has been widely utilized as a technology capable of measuring a microscopic 3D shape of atomic order. However, because scanning is performed by detecting deformation or an oscillating state to/of a cantilever while a contact force is being measured between a probe and a sample, the following problem occurs if the sample is electrically charged: the charge influences deformation or vibration state of the cantilever, causing an error in a shape measurement result by SPM.
For example, National Publication of International Patent Application Publication No. 2001-522045 (Patent Document 1) describes an apparatus for measuring charge distribution of a sample. In addition, Japanese Patent Laid-Open Publication No. 8-136552 (Patent Document 2) describes an atomic force microscope with a voltage control unit for applying a voltage to a cantilever and/or a sample and a similar type of scanning probe microscope and discloses that an interaction such as an electrostatic force which becomes noise in measurements can be canceled by applying voltage at approach by a coarse motion between the cantilever and the sample.
As described above, conventional technologies have the following problem: an error occurs in a measurement result of SPM due to an influence of electrostatic charge of a sample. Moreover, an object of the invention of National Publication of International Patent Application Publication No. 2001-522045 (Patent Document 1) described above is to measure charge distribution without measuring the shape of a sample and has not disclosed a method for accurately measuring the shape of a sample by relieving an influence of electrostatic charges. On the other hand, the invention of Japanese Patent Laid-Open Publication No. 8-136552 (Patent Document 2) simply compensates for interaction such as an electrostatic force at approach by a coarse motion and cannot accurately measure the shape of a sample with charge distribution taken into consideration.
In view of such problems, it is an object of the present invention to provide a method for obtaining an accurate measurement result by SPM without influences of electrostatic charge distribution of the sample.
Moreover, it is another object of the present invention to prevent a sample or a probe from being damaged by discharge between the sample and the probe.
It is yet another object of the present invention to prevent a probe and a sample from being damaged by discharge between the probe and the sample by issuing an alarm and stopping scanning if voltage adjustment amount is in excess of an allowable value during scanning.